Effects of simulated motion frequency related to road quality on the welfare and recovery of transported largemouth bass (Micropterus salmoides)

Abstract

Farmed fish are commonly transported between various facilities by road vehicles, resulting in inevitable exposure to uncontrolled and oscillatory movements, likely exacerbated by poor road conditions. The effect of road quality on livestock has been studied during live transport, but research into the impact of motion has been rarely examined with fish. This study investigated the effects of different motion frequencies related to road quality on the welfare and recovery of largemouth bass (Micropterus salmoides). Three motion frequencies were examined in this study using a non-transported control, a simulated “rough” transport treatment, and a simulated “smooth” transport treatment. Live transport was carried out for 3 h using a motion simulation platform with a movement frequency of 1.0 and 1.8 Hz for the smooth and rough treatment, respectively. Control fish were kept in static tanks for the same duration to obtain basal physiology, behaviour, and flesh quality. Water parameters were measured before and immediately after simulated transport in all groups. Behavioural, physiological, and muscle parameters were measured before simulated transport, as well as 0 h and 24 h post-transport. Total ammonia nitrogen levels increased in all treatments over time (p < 0.001), with significantly higher values observed in transported groups. Non-transported fish displayed increased biting (p = 0.025), chasing (p = 0.010), and threatening (p = 0.003) behaviour over time, suggesting potential fasting and confinement stress. During the post-transport period, a significant main effect of treatment and timepoint on freezing and thigmotaxis behaviour was found, with an increase in these behaviours over time and significantly higher levels between control and smooth transported groups. Nevertheless, aggressive behaviours were affected only by timepoint, with an increase observed between 0 h and 24 h post-transport. Neither plasma biochemical indicators nor flesh quality differed between treatments, while a significant effect of timepoint was found for plasma glucose (p = 0.045), plasma lactate (p = 0.021), and muscle pH (p < 0.001). Our study consequently did not find rough transport to impact fish physiology and flesh quality more than smooth transport, but behavioural results suggest there was a strong combined effect of fasting, exposure to a novel environment, and confinement over time. Future research would be valuable to study these effects on the welfare of transported bass, allowing for a longer recovery time and the use of potential mitigation options such as environmental enrichment.